title: Concurrent maturation of inner hair cell synaptic Ca2+ influx and auditory nerve spontaneous activity around hearing onset in mice.
abstract: Hearing over a wide range of sound intensities is thought to require complementary coding by functionally diverse spiral ganglion neurons (SGNs), each changing activity only over a subrange. The foundations of SGN diversity are not well understood but likely include differences among their inputs: the presynaptic active zones (AZs) of inner hair cells (IHCs). Here we studied one candidate mechanism for causing SGN diversity-heterogeneity of Ca(2+) influx among the AZs of IHCs-during postnatal development of the mouse cochlea. Ca(2+) imaging revealed a change from regenerative to graded synaptic Ca(2+) signaling after the onset of hearing, when in vivo SGN spike timing changed from patterned to Poissonian. Furthermore, we detected the concurrent emergence of stronger synaptic Ca(2+) signals in IHCs and higher spontaneous spike rates in SGNs. The strengthening of Ca(2+) signaling at a subset of AZs primarily reflected a gain of Ca(2+) channels. We hypothesize that the number of Ca(2+) channels at each IHC AZ critically determines the firing properties of its corresponding SGN and propose that AZ heterogeneity enables IHCs to decompose auditory information into functionally diverse SGNs.
authors.affiliation: InnerEarLab, Auditory Systems Physiology Group, Department of Otolaryngology, and Collaborative Research Center 889, University Medical Center Göttingen, D-37099 Göttingen, Germany.
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Wong
authors.forename: Zhizi
authors.initials: Z
authors.lastname: Jing
authors.forename: Mark A
authors.initials: MA
authors.lastname: Rutherford
authors.forename: Thomas
authors.initials: T
authors.lastname: Frank
authors.forename: Nicola
authors.initials: N
authors.lastname: Strenzke
authors.forename: Tobias
authors.initials: T
authors.lastname: Moser
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D003051:Cochlea / Q000254:growth & development / Q000294:innervation; D003056:Cochlear Nerve / Q000254:growth & development / Q000502:physiology*; D017626:Cochlear Nucleus / Q000166:cytology / Q000502:physiology; D003198:Computer Simulation; D055724:Electrophysiological Phenomena; D005260:Female; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008959:Models, Neurological; D009154:Mutation / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics; D018408:Patch-Clamp Techniques; D017661:Receptors, Presynaptic / Q000502:physiology; D013136:Spiral Ganglion / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D013347:Subcellular Fractions / Q000502:physiology
chemical_list: C498441:Bsn protein, mouse; D015220:Calcium Channels; D009419:Nerve Tissue Proteins; D017661:Receptors, Presynaptic; D002118:Calcium